1. Field of the Invention
Exemplary embodiments disclosed herein generally relate to electric arc engine welders, including those employing a welding gun for use in a welding operation and a wire feeder for supplying a consumable welding wire electrode to the welding gun. More particularly, exemplary embodiments disclosed herein relate to improved contactor assemblies for welding wire feeders. The embodiments find particular application as (or in) portable electric arc engine welders, often used when the location of the welding operation is not expected to remain constant, such as, for example, welding operations at job sites which change regularly or welding operations covering large areas at a single job site. It is to be appreciated, however, that the exemplary embodiments discussed herein are also amenable to other like applications.
2. Discussion of the Art
Electric arc engine welders are generally well known. Typically, in electric arc welders, a power source passes current between an electrode and a work piece. Often, the electrode is a continuous welding wire drawn from a supply of welding wire, such as a drum or reel, which is passed through a contact tip or gun on its way to being melted and deposited onto the work piece. The gun can be provided with a selectively operable switch for applying welding power from the power source to the electrode (i.e., the wire) for establishing an arc between an exposed portion of the electrode and the work piece. Wire feeders are often used to advance the welding wire, preferably in a consistent and controllable manner, to the welding gun for use in the welding operation. Welding wire feeders can be manufactured in several forms, each optimized for a specific application. Common classifications of wire feeders include robotic wire feeders, portable wire feeders, tractor wire feeders and bench mount wire feeders.
Portable wire feeders are often used when the location of the welding operation or operations is likely to change or does not always remain constant (e.g., shipyards). This might include, for example, welding operations at job sites that change day-to-day or welding operations that cover a large area at a single job site. Examples of portable wire feeders are generally taught in the following U.S. patents: Bellefleur U.S. Pat. No. 4,665,300; Rybicki U.S. Pat. No. 6,213,375; Kroll U.S. Pat. No. 4,508,954; Chandler U.S. Pat. No. 6,225,596; Miller U.S. Pat. No. 5,410,126; Grimm U.S. Pat. No. 5,836,539; and Luo U.S. Pat. No. 6,705,563, all expressly incorporated herein by reference.
Preferably, portable wire feeders are able to supply their respective welding operations with welding wire in a manner much like that of a conventional stationary wire feeder. This is often more difficult in the portable wire feeder because it is likely to be subjected to repeated movement and used in connection with a wide range of work environments, many of which can be severe. In contrast, conventional stationary wire feeders are often used in controlled and unchanging environments, such as a work shop or factory floor. In addition to functioning like a stationary wire feeder, the portable wire feeder is preferably compact and lightweight enabling it to be more easily moved and used in confined work areas. Other desirable characteristics of portable wire feeders are ruggedness and durability.
In one conventional welding arrangement, a portable wire feeder is connected to a remotely positioned power source through a power source cable, also known as an electrode cable. The wire feeder is additionally connected to a welding gun by a guide hose. A motorized feeding system in the wire feeder employs rollers to advance or pay welding electrode wire from a supply of wire (often a spool of wire) through the guide hose to the welding gun. For this purpose, the guide hose can include an internal tube for transporting the wire from the feeder to the gun, in addition to electrical wiring for providing power (such as control circuitry) to the gun. Optionally, the guide hose can further include passageways for transporting shielding gas to the gun and/or for circulating cooling fluid through or to the gun.
More particularly, portable wire feeders typically include a housing or enclosure with an input crimp or lug terminal for connecting the power source cable to a bus bar, and an output connected to the guide hose to which welding power from the power source is provided together with the welding wire driven by the motorized wire feeding mechanism. Portable wire feeders, including the motorized wire feeding system and control circuitry thereof, can be powered by the arc current from the power source. Portable feeders typically include a means for switching the arc current to the welding guide hose, such as a contactor. A trigger on the gun closes a switch to initiate the welding operation, which causes the contactor to provide welding current to the guide hose and also starts the motor for feeding wire to the guide hose. The welding arc current flows through and is switched on and off by the contactor of the portable wire feeder.
Over time, contacts of the contactor, also referred to herein as an electromechanical switch, deteriorate from the arcing and from heating. When this occurs, heretofore the whole contactor was replaced as a complete unit. This had been considered desirable in the past because of the reduced inventory of parts required to service a wire feeder and the simplification of the replacement process. However, there is a sizable segment of the wire feeder market that has the skills necessary to do a contactor repair on a part-by-part basis and/or is willing to stock replacement parts, including the several parts that comprise a contactor assembly. Often, these users are sensitive to the replacement costs of the contactor assembly and are continuously looking for cost savings.
Thus, for example, when the contacts of a contactor assembly are worn, and the remainder of the contactor assembly is in good condition, it may be desirable to replace only the contacts. Typically, the coil and frame of the contactor assembly have longer useful lives than the contacts and may not necessarily require replacement when the contacts initially fail. Thus, there is a need for improved portable wire feeders and contactor assemblies therefore to facilitate replacement of selected parts of the contactor assembly. This would enable a customer to replace only select components of the contactor assembly when it fails, rather than replacing the entire contractor assembly as a unitary component. Advantages to be gained include the lowering of replacement costs associated with failing contactor assemblies, as well as reducing environmental waste.